HP 5383A / Agilent 5383A 520 MHz Frequency Counter with 9 Digit Display with OPT 001 TCXO, See Description

Frequency Range: 10 Hz to 520 MHz.
Sensitivity: 1 Mohm 25 mV rms - 20 Hz to 10 MHZ, 50 mV rms - 10 HZ to 50 MHz & 50 ohm 25 mV rms - 20 Hz to 520 MHz.
Input Impedance: Selectable 1 M ohm, <40 pF or 50 ohm
Input Attenuation: 1 Mohm x 1, x 10; 50ohm x 1 - fuse protected.
Gate Time: 0.1 second, 1 second & 10 Seconds.

OPTION  001:  TCXO, temperature compensated crystal oscillator time base)

NOTE: We have a few of these and are selling them from cosmetic best to worst on a first come, best cosmetics basis. The one pictured is actually one of the worst, cosmetically - the wrinkles you see on the front is strictly the top layer, plastic film. It is not cracked. Some are more yellow with fewer wrinkles.